Process for producing olefinic compounds



-. dnsation. The; a

' Patented May 15,945

- Miller Swaney, Cranford; and Leland K. I Beach, Elizabeth, N. 'J., assignors, by meme assignments, to Jasco, Incorporated, .a corporav tion of No Drawing.

"Application December Serial No. amaze I 1 11 Claims. (Cl. 260-480) v The present; invention relates to a process for the production of unsaturated compounds by the dehydrohalogenation of halogenated hydrocarbons. In particular, the invention is concerned with the production of aliphatic didlefins by the dehydrohalogenation or dihaloparaffins and more-particularly, to the production of hutadiene from dichlorobutane.

The thermal decomposition of dihaloparafiins to yield the corresponding diolefin and hydrogen halideis known to the art. However, the process is so replete with manipulative difficulties that it has never come into general use. 'The thermal decomposition of the dih'alides of paraflhr hydrocarbons occurs at such an elevated temperature that the choice ofmaterials capable. otretainthermally decomposed.','Ihe gases leaving the reactor were passed: over. a cooling-surface into a. water scrubber to remove hydrogenv chloride by absorption,- and to condense monochlorobutenes and unreacted dichlorobutane; the gases then passing through a drying tower and into a dry ice-cooled receiver to condense butadiene and other C4 hydrocarbons. 'I'hecondensates were fractionated taking overhead a C4 cut, namely,

that fraction boiling between --10 and +10 C.,

amounting. to a 62% yield based'upon the dichlorobutane feed which, upon analysis, showed a 90% butadiene. content, the remainder of the.

" condensate being butylenes. Accompanying this ing their tensile strength at such temperatures with which to make the reactor is exceedingly during the reaction is highly' reactive at the high temperature, corroding metal reactorsand formlimited; Also, the hydrogen halide liberated in; salts which are volatile at that temperature,

ther decompose, forming a large amount of lower molecular weight hydrocarbons and ultimately hydrogen and carbon. The products of this secondary decomposition not only dilute or con-- taminate the desired substance formed, thus."

yielding an undesirable product, but reduce the yield based upon the halogenated hydrocarbon charge. 1

.In' general, the procedure'is to vaporize the halohydrocarbon and pass the vaporsthrough areactor tube heated to a temperature or from 500 C. to 700 -C.,' and to pass the gases leaving.

the reactor through a recovery system where the.

unsaturated product is separated irom the gases 0 by removal or hydrogen halide followed by coned product is then recovered from the condensateby distillation and conden'sation. r

;- The following examples are illustrative of the .ileiiclencies present'inthe prior art processes:

- e sample 701' -2 ,3-dichlorobutane (B. P. 114-, 118? C.) ,was vaporized and passed through an electrically heated 1" inside diameter fused. quarts reaction tube maintained at a temperature of 600C at such. a rate-that the reaction time or contact was J-1-2 seconds. Under these l to otthe-dichlorobutant was but whichcondense in the cooler portion of the reactor. forming an obstruction which soon stops the flow of materiaL- Furthermore, the hydro- 25 carbons formed during the reaction tend to furrun was the formation of considerable light-ends gases. and considerable sooty carbon formed in the reaction tube. I

A sample of 2,3-dichlorobutane feed stock was vaporized and passed through a heated-1" inside diameter nickel tubeat 600 C. and about 3,- seconds contact time.

after a short time, 323 mol percent of the feed stock being recovered in the \form of carbon,

Large amounts of light-ends were produced and 1 the.C4-Cut obtained by fractionating, the crude- 'product' contained only 50% butadiene, the remainder'bing principally butylenes.

I EX MPLE 3 I {A quantity of 2,3-dichlorobutane feed stock I was vaporizedand passedthrough a 1" inside diameter. copper tube heated to 600 C. a reaction time of contact of a seconds being maintained. During this runsome light-ends were produced alongwithoi'l mol per cent of. carbonization occurring in the reaction tube.; The

butadienecontent of the 04 cut was EXAMPLE 4 Feedstock of 2,3-dichlorobutane was vaporized.

andpassed through aisteel alloy tube (12% chromium, remainder iron) heated to 600 C., the V reaction time .01 contact being held at. 2seconds.

' Arf appreciable-quanti'ty or light-ends was formed during the' experiment-and the amount of feed beinglargely butylenes.

conv'e'rted' to carbon in the reaction tube was I approximately 0.1 mol per. cent. The purity of the-C4 cut was 75 butadiene, the j'remainder i-EXAMPLES Feed stock or 2,3-dichlorobutane was vaporized and Carboni zation was so severe that the reaction tube was nearly plugged passedthrough asteel'alloy tube 17% chromium, remainder iron) heated to 600 C., the contact time of the reaction being maintained at 1.2 seconds. Appreciable light ends were formed along with 0.1 mol per cent of carbon inthe tube. The purity of the C4 cut was 86% butadiene, the remainder bein-g largely butylenes.

' EXAMPLE 6 A sample .of feed stock, of 2,3-dichlorobutane was vaporized and passed through a reaction tube composed of 28% chromium; a trace of nickel, and the remainder iron. The reaction tube was heated to 600 C. and the reaction time of contact was 4 seconds; Some light-ends were produced during the run, and the amount of feed converted to carbon in the tube was 0.1 mol per cent. The purity of the C4 cut was only 82% butadiene. I 3

According to'the present invention, in the dehydrohalogenation of halogenated hydrocarbons, such as the conversion of mono, di, tri or higher halogenated aliphatic or cycle aliphatic. hydrocarbons to olefins, mono-halogenated oleiins, diolefins and halogenated diolefins, e. g., monochlorobutane orpentane to butylene and pentylene respectively; dichlorobutane or pentane to butadiene and pentadienes; trichlorobutane to dichlorobutylene or chlorobutadiene, etc, carbonization and the production of undesirable low EXAMPLE 7 Feed stock of2,3-dichlorobutane was vaporized and passed through a reaction tube consisting of an Inconel outer shell lined with a. 0.003 inch thickness of'platinum. The tube was maintained at a temperature of 600 C and the feed ratefinish. The or cut analyzed 97 1,3-butadiene.

EXAMPLE 8 A sample of 2,3-dichlorobutane feed stock was vaporized and passed at constant rate through a reaction tube heated to 600-650 C. The reaction tube consisted of an Inconel outer shell I For the purpose of ready, comparison, the following table is included:

TABLE Comparative data on. platinum versus other tribes in ,dehudrol alogenation .Exam le Tcmp.oi Contact Butadiene Tube material mom! time Carbomtation ,Llghtends A C'. Seam Per cent I Fud quartz. .2 600 1-2 Consldcrable-. Considcrable. 90 II Nickel u 600 3 32811201 per Abundant..-..-.

. can I TIT Copper 600 2 v 0.1 1:101 per Appreciable.-. 90

. Y I can IV Cr-steel 600 2 .do do 75 ,V- 17 Cr-steel 600 1.2 do 86 VI 28 o Cr-steel, trace of Ni.. I 600 4 -..do..-. 82 VII In onel tube lined with 0.003 inch pleti- 600 1-2 N ono.. None 97 num.

VIII..-. Inconel tube lined with silver" 000-650 1 Very slight--. ...-do 04.7

molecular weight hydrocarbons are substantially avoided and products substantially pure are obtained by conducting the reaction under suitable conditions'of time of contact and temperature in a reactor. constructed oi a noble'metal such as platinum or silver, etc.

, Thus, aliphatic dienes such as butadiene, pen- .tadienes, hexadienes, etc., are produced from'the corresponding 'dihalide's of the saturated aliphatic hydrocarbons such as dichloro or dibromo butane, dichlor or'dibromo pentane, etc. by passin'gthe vaporizeddihalides thru a heated reac-g tion tube formed from a noble metal at a temperature from about 400 to 700 C.', and suitable purifying the diene by fractionation. The reac What is claimed is:'

1. The process of producing oleiinic compounds which comprisespassing halogenated hydrocarv sulting gases."

' contact time, condensing the resulting gases and" tion may be -carried out atyarious pressures ranging from subatmospheric' pressures in the order of 100 mm. of Hg to superatmospheric pressures of 1000 mm. of Hg 'or higher.

It is not necessaryto use a reactor having solid walls of noble metal. A reaction tube consisting of an Inconel. or'other alloy metal outer shell lined with an inner lining of noble metal of'from 0.001 to 0.010 inch in thickness is quite satisfac;

I The following examples are given for the purpose of illustrating the invention:

2. The process of producing olefinic compounds which comprises passing halogenated hydrocarbon vapors 'thru a platinum reactor heated to a temperature between 400 C. and 700 C. and.

recovering the 'olefinic compounds from the resulting gases.

3. The process of producing olefinic compounds which comprises passing halogenated 'hydrocarbon vapors 'thru a silver reactor heated to a temperature between 400 C. and 700C. and removing the oleflnic compounds from the resulting ases. 1

4.The-process of producing dioleflns which. comprises passing dihaloparamn vapors thru a noble metal reactor heated to a; temperature of 400 C. to 700 C. and recovering thedioleflns from the resulting gases.

5. The -processof claim 4 in'which a platinum reactor is used.

. reactor is used.

6. The process of claim 4-in which a silver ass-macs I 5 3 'l. The rocess of producing butsdiene which comprises passing dichlorobutane vapors thru a. noble metal reactor heated to a temperature between 500 C. and 700 C. andrecoverms the mitedienetromtheresultinggases.

8. A process 01' claim I in-which a platinum reactor is used.

9. Aprocess of ciaimjlin which a silver reactor isused.

lined reactor isused.

10. The W of producing butadiene which comprises dichlorobutane vapors thrua.

platinum reactor heated to a temperature of 600 0., and isolating the tadiene from there- 11. m processot mimic in which a platinum imm'mmswmm, mumnx. amen. 

